Electrostatic developing apparatus



Feb. 25, 1964 E, ERY 3,122,453

ELECTROSTATIC DEVELOPING APPARATUS Filed Dec. 29, 1960 IN VEN TOR. ELWOOD T. MONTGOMERY AGENT United States Patent 0 Dec. 2a, was, Ser. No. vases 9 Claims- (l. ire-s37 This invention relates to electrostatic apparatus and more particularly to apparatus :for visibly developing information electrostatically recorded on a recording me dium.

T he electrostatic recording process consists broadly of three steps. The first step comprises establishing, or printing, electrically charged areas on selected portions or" a record medium which are representative or" information or designs. The second step consists of developing such charged areas on the record medium by means of an inking powder thus to make them visible. The third step, which is optional, consists in fixing, or rendering such developed areas substantially permanent. In the electrostatic recording process, these three steps take place sequentially and at physically separate locations. We are primarily concerned here with the second step.

The record medium is preferably made of a backing layer, or web of paper, on one side of which is bonded a thin layer of high resistivity, or dielectric material. T re web of paper is moved through the printing apparatus where the electrically charged areas are established and from this station it passes to the inking and fixing stations sequentially.

During the developing or inking of the latent electrostatic image, developing powder or ink will adhere to the electrostatic charged areas, thus to make them visible. Unfortunately under some conditions ink will also adhere to the background or uncharged portions of the record material. 1 is is an undesirable condition as it tends to obscure the desired information.

Apparatus has been provided for the purpose of developing such latent electrostatic images without leaving background ink during normal operation, and in this regard reference may be had to the co-pending application filed jointly in the names or" George A. Harris and the inventor of the present apparatus on lanuary 28, 1959, bearing Serial No. 789,725, now US. Patent No. 2,998,802, with the title Electrostatic Developing Apparatus, and assigned to the assignee of the present invention. The inking apparatus described in this co-pending application is quite efifective for the visible development of clean electrostatic images during normal continuous operation thereof. It has one disadvantage in that during the time the web of record material is in a static or idle condition in the apparatus, the ink has a tendency to adhere to the web so tenaciously as to prevent associated suction cleaning apparatus from completely removing unwanted ink from the area in contact with the ink during the period in which the web was motionless. This has resulted in an undesirable gray band extending transversely across the web.

It is an important object of the present invention to provide apparatus for developing or inking electrostatically recorded information or images in a manner overcoming the above-mentioned disadvantages.

More specifically, it is an object of the present inven- Patented Feb. 25, 1964 tion to provide such apparatus permitting ink adhering to the uncharged or background areas of the recording medium to be cleanly removed under all conditions of operation.

More specifically it is an object of the invention to provide an electrostatic developing apparatus which is of inexpensive construction and which has no moving operational parts.

in accordance with the above objects and first briefly described, the invention comprises apparatus through which an electrostatically charged web of record material may be passed for developing the charged areas with inking powder which is maintained in contact with the charged side of the web. The inking powder is housed in a container having a trough in sich ink is maintained at a substantially constant level by gravity feed of the ink from the container thus to maintain a predetermined quantity of the ink lightly urged against the recording medium whereby it may be attracted to the latent electrostatic ima e in a manner to visibly develop the image, but without causing the ink to :e to the unchargc or background area of the record medium in a preventing its easy removal by an associated sucron cleaning device positioned closely adjacent the record medium.

Other objects and attendant advantages of this inven tion will be readily appreciated as the sar 1e becomes better understood by reference to the following detailed description when considered with the accompanying drawings wherein:

l is a top plan View of the apparatus embodying the preferred form of the invention;

FIG. 2 is a sectional view taken along the line 22 of FIG. 1; and

FIG. 3 is a fragmentary sectional view on an enlarged scale showing the movement of the record medium through the apparatus in its area of contact with the powdered ink.

Referring now to the drawing illustrating the preferred form of the invention, it will be seen that the apparatus comprises a housing or container including a base JLLJ member or bottom wall 11 and an inverted cup-shaped member 12, cooperating to form a chamber for receiving a quantity of powdered ink 13.

The base member 11 comprises a portion of the overall electrostatic apparatus, as shown here, but may, if desired, be a separate element of thin walled construction for mounting on the machine. The top surface of the base member ill slopes downwardly to the left at an angle approximating 36 to terminate in closely spaced relation with an anvil or guide member 16 over which the record member or web 18 is fed in the direction indicated by the arrow 2%. The cup-shaped member 12 is formed by a top wall 22 and downwardly extending side walls 24. The lower edges of these side walls abut and are suitably secured to the surface of base member 11 except at the lower edge 26 of the front wall 24a where it is spaced from the base member to provide a passageway 27 for the powdered ink 13 to llow from the container. A slide member or gate is adjustably positioned over the passageway as by slots 29 and screws 3tl only one or" which is shown-to provide for adjusting the rate of ink-flow through the passageway.

The top wall 22 of the hopper is provided with a filling aperture 31 having a closure member or cover 32 releasably secured thereover as by a spring member 34 rotatably secured thereto as by the screw 26. The cover is released by rotating the spring member 34 in either direction to a degree suflicient to remove the ends 38 thereof from engagement in the grooves pins 41 being provided for this purpose, after which it may be pivoted upwardly about the hinge 42 so that the ink supply may be replenished when necessary. Preferably the cover is sealed against the top Wall, as by the gasket 43, in which case a vent opening 44 is provided to admit air to the upper portion of the chamber to equalize the pressure on both sides of the ink supply so that the ink can flow freely during operation of the machine.

Extending forwardly of the front wall 24a of container 12, and preferably integral therewith, as shown, is a top wall 45 and opposite side walls 46, only one of which is shown, cooperating with the lower lefthand end 11a of base member 11 and guide member 16 to form a substantially enclosed trough 47 for receiving the ink 26 as it flows through passageway 27. The gate 28 controls the flow of ink into the trough to the level desired but in any case to an extent suflicient to engage the record medium as it passes through the trough over the guide member 16. Under high speed operation it may be desirable to have a greater quantity of ink in contact with the record member, in which case the gate is raised slightly. It will be seen that the walls 45 and 45 terminate closely adjacent to but spaced from the guide member *16 an amount equal to the space between the lower end 11a of base member 11 and the guide member 16. The portion of this opening extending across the end 11a of base member 11 and up the edges of side walls 46 is closed by a sealing element 48 which is secured to the edges of these members as by' screws 56), only one of which is shown, thus to prevent leakage of the ink from the trough. The sealing element may be formed of any suitable sealing material having suflicient rigidity to maintain its shape yet flexible enough to permit the Web of recording material to move freely over the guide member 16.

Suitably secured as by screws 52 on the top wall 45 of the trough 47 is the nozzle 53 of a device which is connected to a suitable source of suction pressure, not shown, as by the flexible tube 56. As shown here, the inlet opening 58 of the nozzle is positioned closely adjacent the guide member 16 but with sufficient clearance to permit the record medium to pass between these two members whereby, as shown in FIG. 3, excess background ink adhering to the web as it moves through the trough 47 may be sucked into the nozzle thus to be removed from the web.

In operation of the apparatus as hereinabove described, a supply of ink is poured into the hopper 12 through the opening 31 after which the cover 32 is moved into position to close the opening. Ink 26 will flow down the sloping top surface 14 of base member 11, through the opening 27, into the hopper 47 and against the record member if one happens to be present, or against the guide member 16 if a record member is not present. In either case his prevented from spilling out of the hopper by the sealing member 48 which will be resiliently urged either against the record member or the guide member, as the case may be.

Assuming initially that no record member is present, one is fed through the inlet opening 60 and upwardly through trough 47 over guide member 16, out of outlet opening 61 and between drive rollers 62. Cooperating with the drive rollers 62 is a pair of rollers 64 at the lower end of guide member 16 to maintain the record member tightly over the guide member as it passes through the trough either continuously or incrementally.

As the electrostatically charged record medium moves through the trough 47 ink particles will adhere to the latent image electrostatically recorded on the record memher thus visibly developing these images. Only a small portion or layer of the ink 13a in the trough 47 is in contact with the record member. As shown in FEGS. 2 and 3, this portion or layer of ink is formed by the upper surface of the ink in the trough 47, as established by the gate 28, and a lower surface of the ink established by the upper edge of that portion of the sealing member 48, shown in section, which extends across the end 11a of the base member 11. As the ink adheres to the electrostatic charged areas of the record medium diminishing the supply of ink in the trough, it will be constantly replenished from the ink supply within the chamber 12. Because of the upward movement of the record medium 20 the ink Will assume the condition illustrated in FIG. 2 wherein its top surface is angled downwardly a degree or so from the area in which it is in contact with the record medium to the lower edge 28a of slide member or gate 28. This condition and the height of the ink supply in trough 47 will be maintained substantially constant during the operation of the apparatus and for so long a time as the ink level in chamber 12 is maintained above the edge 28a of gate 28, thus to maintain the ink in contact with the record medium at a substantially constantthough lightpressure which in every case is insufficient to cause the ink to adhere to the record medium with sufiicient pressure to prevent the suction cleaning apparatus from completely removing it from the background or unrecorded areas of the record member. This condition is more clearly illustrated in FIG. 3 which shows the ink adhering to the record member as it moves upwardly in the direction of the arrow and the excess being removed by the nozzle 53.

Thus it is seen that the present invention overcomes the difficulties in previous devices of this kind to provide apparatus which will develop a clean copy of information clectrostatically recorded on a web of recording medium under all conditions of operation of the recording machine.

What is claimed is:

1. Apparatus for developing images electrostatically recorded on a record medium comprising: a container for holding a supply of inking powder and provided with a downwardly extending bottom surface; and a closed-bottom trough connected to said container, said trough and said container being in open communication with each other through a passageway common to both, whereby ink will flow from said container down said bottom surface and into said trough to maintain an ink supply in said trough at a level regulated by the size of said passageway, said trough having inlet and outlet openings through which the record medium may be fed with its electrostatically charged areas in contact with the inking powder in the trough as the record medium passes through the trough thus to develop the said images; said troughhaving a downwardly extending bottom surface onto which the ink flows from the bottom surface of said container in such manner as to maintain the ink therein against said record medium at a constant light pressure to prevent excess ink adhering to said record medium in a manner preventing its easy removal.

2. Apparatus for developing images electrostatically recorded on a record medium comprising: a container for holding a supply of inking powder and provided with a sloping bottom surface; a closed-bottom trough connected to said container, said trough and said container being in open communication with each other through a passageway common to both, whereby ink will flow from said container down said bottom surface and into said trough to maintain an ink supply in said trough at a level regulated by the size of said passageway, said trough having inlet and outlet openings through which the record medium may be fed with its electrostatically charged areas in contact with the inking powder in the trough as the record medium passes through the trough thus to develop the said images; and means sealing said inlet opening in a manner to prevent ink sp g from said trough whether or not the record medium passing therethrough.

3. Apparatus for developing images electrostatically recorded on one side of a record medium comprising: a container for holding a supply of inking powder and provided wi h an inclined bottom Wall; a closed-bottom trough connected to said container, said trough and said container being in open communication with each other through a passageway common to both, whereby ink will fiow from said container down said bottom wall and into said trough to ntain an ink supply in said trough at a level regulated by the size of said passageway, aid trough having inlet and outlet openin s through which the record medium may be fed with its electrostatically charged side contact with the inking powder in the trough as the record medium passes through the trough thus to develop the said images; flexible means sealing said inlet opening in a manner to prevent ink spilling from said trough whether or not a record medium is present; and means positioned adjacent said outlet opening to remove excess ink from the surface of record medium.

4. Apparatus for developing images electrostatically recorded on one side of a record medium comprising: a vertically disposed container for hol ing a supply of inking powder and having side walls, and a bottom Wall sloping toward one side wall; a closed-bottom trough connected to the exterior of said container at the bottom of said one side wall, said trou h and said container being in open communication with each other by means of a passageway rough said one side wall and common to both, whereby ink will flow from said container down said bottom wall and into said trough to maintain an ink supply in said trough at a level regulated by the top of said passageway, said trough having inlet and outlet openings through which the record medium be fed ch its electrostatically charged side in contact with the ir ring powder in said trough as the record medium passes through the trough thus to develop the said images; fiexible means sealing said inlet opening in a manner to prevent ink spilling from said trough whether or not a record medium is present; and suction cleaning means positioned adjacent said outlet opening to remove excess ink from the developed surface of said record medium.

5. Apparatus for developing images electrostatically recorded on one side of a record medium comprising: a conta ner for holding a supply of inking powder, said con ier having side walls, and a bottom wall sloping downwardly to one wall of said side walls; a closedbottom trough connected to the outside of said one Wall and adjacent the bottom thereof; said one wall being common to both the container and the trough; said trough and said container being in open communication with each other throu h an opening in said one wall whereby ink will flow from said conta' down said bottom wall and into said trough to maint m an ink supply in said trough at a predetermined level regulated by the height of said opening; said trough hav lg inlet and outlet openings in bottom top walls thereof respectively and adjacent a trough side wall opposite said one wall whereby said record medium may be fed through said trough over said trough side wall with its electrostatically charged side in contact with said inking powder as the record medium passes through the trough t?" to develop the said images; flexible means ext 1g across said inlet ooening to seal it against 1 sgillint rrom said opening w r or r. t a record medium is being fed therethrough.

6. Apparatus for developing images electrostatically recorded on one side of a record medium comp a vertically positioned container or holding a s inking powder, said container havin side walls, and a bottom wall sloping downwardly to the bot" it wall of said side walls; a closed-bottom trough cormected to the outside or" said one wall adjacent the be or thereof; said one wall being common to both the container and 5 the trough; said trough and said container being in ope. communication with each other through an opening extending across the bottom of said one wall whereby ink will flow from said container down said bottom wall and into said trough to maintain an ink supply in said trough a predetermined level regulated by the height of said opening; means to adjust the height of said opening; said trough having inlet and outlet openings in bottom and top Walls respectively thereof and at a side wall opposite said one wall whereby said record medium may be fed through said trough over said trough side wall with its electrostatically charged side in contact with said inking powder as the record medium passes through the trough thus to develop the said images; flexible means extending across said inlet opening to seal it against ink spilling from said opening whether or not a record medium is being fed therethrough; and means positioned adjacent said outlet opening to remove excess ink adhering to said record medium.

7. Apparatus for developing images electrostatically recorded on one side of a record medium comprising: a container for holding a supply of inking powder; said container having side walls, an apertured top wall, a closure member for said aperture, and a bottom wall sloping downwardly to the bottom of one wall or" said side walls; a closed-bottom trough connected to the outside of said one Wall adjacent the bottom thereof, said one wall being common to both the container and the trough; said trough and said container being in open communication with each other th ough an opening in said one wall whereby ink will ,tlow from said container down said bottom wall and into said trough to maintain an ink supply in said trough at a predetermined level regulated by the height or" said opening; means to adjust the height of said opening; said trough having inlet and outlet openings in bottom and top walls respectively thereof and at a side wall opposite said one wall whereby said record medium may be fed through said trough over said trough side wall th its electrostatically charged side in contact with said inking powder as the record medium passes through the trough thus to develop the said images; said trough having a sloping bottom wall coplanar with said bottom wall of the con tainer onto which the ink flows from the container in such manner as to maintain the ink therein against said record medium at a constant light pressure to prevent excess ink adhering to said record medium in a manner preventing its easy removal; flexible means extending across said inlet opening to seal it against in c spilling from said opening Whether or not a record medium is being fed therethrough; and means positioned adjacent said outlet opening to remove excess ink adhering to said record medium.

8. Apparatus for developing images electrostatically recorded on a record medium comprising: a contains for hold ng a supply of inking powder and provided ith a sloping bottom surface, and a hollow substantially closed trough connected to said container, said trough and said container being in open communication with each other through a passageway common to both and adjustable in size, whereby ink will flow from said container down said bottom suriace and into said trough to maintain an ink supply in said trough at a level lower than the top or the trough determined by the size of said passageway and defining the upper unrestricted surface of a layer of ink in the trough; means establishing the bottom surface of said ink layer at a level above the References Cited in the file of this patent UNITED STATES PATENTS Robinson Apr. 23, 1940 Lipsius Aug. 7, 1956 Olden June 30, 1959 Stvrakis et al Nov. 3, 1959 Jones et a1 June 12. 1962 

1. APPARATUS FOR DEVELOPING IMAGES ELECTROSTATICALLY RECORDED ON A RECORD MEDIUM COMPRISING: A CONTAINER FOR HOLDING A SUPPLY OF INKING POWDER AND PROVIDED WITH A DOWNWARDLY EXTENDING BOTTOM SURFACE; AND A CLOSED-BOTTOM TROUGH CONNECTED TO SAID CONTAINER, SAID TROUGH AND SAID CONTAINER BEING IN OPEN COMMUNICATION WITH EACH OTHER THROUGH A PASSAGEWAY COMMON TO BOTH, WHEREBY INK WILL FLOW FROM SAID CONTAINER DOWN SAID BOTTOM SURFACE AND INTO SAID TROUGH TO MAINTAIN AN INK SUPPLY IN SAID TROUGH AT A LEVEL REGULATED BY THE SIZE OF SAID PASSAGEWAY, SAID TROUGH HAVING INLET AND OUTLET OPENINGS THROUGH WHICH THE RECORD MEDIUM MAY BE FED WITH ITS ELECTROSTATICALLY CHARGED AREAS IN CONTACT WITH THE INKING POWDER IN THE TROUGH AS THE RECORD MEDIUM PASSES THROUGH THE TROUGH THUS TO DEVELOP THE SAID IMAGES; SAID TROUGH HAVING A DOWNWARDLY EXTENDING BOTTOM SURFACE ONTO WHICH THE INK FLOWS FROM THE BOTTOM SURFACE OF SAID CONTAINER IN SUCH MANNER AS TO MAINTAIN THE INK THEREIN AGAINST SAID RECORD MEDIUM AT A CONSTANT LIGHT PRESSURE TO PREVENT EXCESS INK ADHERING TO SAID RECORD MEDIUM IN A MANNER PREVENTING ITS EASY REMOVAL. 